Conventionally, as an electric motor, one disclosed in Patent Literature 1 is known. This electric motor includes a cylindrical inner rotor, a hollow cylindrical stator, a hollow cylindrical outer rotor, and so forth. The inner rotor has a plurality of permanent magnets arranged in the circumferential direction. Further, the stator includes a plurality of armatures. The armatures are circumferentially arranged, and are fixed to each other by a resin mold. The outer roller is formed by winding coils around respective cores formed by laminating a plurality of rings, but the coils are not supplied with electric power. Further, the inner rotor, the stator, and the outer rotor are arranged sequentially from inside, and are rotatable relative to each other.
In the electric motor constructed as above, the stator is supplied with electric power to generate a rotating magnetic field, and accordingly, magnetic poles of the permanent magnets of the inner rotor are attracted or repelled by the magnetic poles of the stator, whereby the inner rotor is caused to rotate synchronously with the rotating magnetic field, while the outer rotor is caused to rotate asynchronously by electromagnetic induction. As described above, the electric motor disclosed in Patent Literature 1 functions not as a synchronous machine but as an induction machine in which the outer rotor is caused to rotate by electromagnetic induction, and hence suffers from the problem of low efficiency.
As an electric motor capable of solving the above problem, the present applicant has already proposed an electric motor disclosed in Patent Literature 2. The electric motor shown in FIGS. 1 to 6 in Patent Literature 2 is a rotating electric motor, and comprises two outer stators arranged on an outer side thereof, inner stators arranged between the two outer stators, and soft magnetic material rotors disposed between the outer and inner stators and each having two rotor sections. A plurality of armatures are arranged at predetermined spaced intervals on each outer stator, and when the electric motor operates, these armatures are provided with electric power such that N poles and S poles are alternately arranged.
Further, also on each inner stator, there are arranged a plurality of armatures at predetermined spaced intervals smaller than the spaced intervals at which the armatures are arranged on each outer stator. When electric power is supplied, the coils of each adjacent three of the armatures on each inner stator are formed as three-phase coils which exhibit U-phase, V-phase, and W-phase, respectively, and generate a moving magnetic field. Furthermore, a plurality of soft magnetic material cores are arranged on each of the two rotor sections of each soft magnetic material rotor at the same spaced intervals as the spaced intervals at which the armatures are arranged on each outer stator. When the positions of magnetic poles generated at the armatures of the outer stators are used as references, the soft magnetic material cores of one of the rotor sections are arranged such that they are displaced by an electrical angle of π/2 from corresponding ones of the soft magnetic material cores of the other rotor section.
In the above electric motor, along with generation of the moving magnetic fields at the inner stator, magnetic circuits are formed between magnetic poles generated at the armatures of the inner stators, the soft magnetic material cores, and the magnetic poles of the armatures of the outer stators, and magnetic force lines acting on the soft magnetic material cores of the two soft magnetic material rotors drive the two rotor sections, that is, the soft magnetic material rotors, for rotation. At this time, the two rotor sections rotate in unison with each other, while alternately repeating respective states in which the magnetic forces acting on the soft magnetic material cores of one of the rotor sections and the magnetic forces acting on the soft magnetic material cores of the other rotor section increase and decrease by turns. As described above, the electric motor functions as a synchronous machine during operation thereof, whereby it is possible to improve the efficiency compared with the electric motor disclosed in Patent Literature 1.
Further, as a magnetic power transmission system corresponding to the magnetic machine, the present applicant has already proposed one disclosed in Patent Literature 3. This magnetic power transmission system has a construction corresponding to a construction formed by replacing the magnetic poles generated at the armatures in Patent Literature 2 with the magnetic poles of permanent magnets.
[Patent Literature 1] Japanese Laid-Open Patent Publication (Kokai) No. H11-341757
[Patent Literature 2] Japanese Laid-Open Patent Publication (Kokai) No. 2008-67592
[Patent Literature 3] Japanese Laid-Open Patent Publication (Kokai) No. 2008-39045